When any type of vehicle is operated at highway speeds, it is desirable to be aware of loss of pressure in one or more of the vehicle tires, particularly from the standpoint of safety. It is known that vehicles become increasingly hard to control as one or more of the tires become soft and, particularly in emergency situations, such reduced control may result in complete loss of control with resultant injury to the occupants of such vehicles and to other vehicles which may be involved in a collision. This condition is particularly serious in heavy duty vehicles and heavily loaded vehicles, such as trucks, busses, or tractor-trailer units.
In addition to personal injury losses, losses may be incurred in the lading in the case of freight-hauling vehicles. Apart from the major losses mentioned above, it is important from the economic standpoint in the operation of a trucking fleet, for example, to maintain proper tire pressure to prevent excessive tread wear. In the case of dual tire wheel units, in particular, excessive tread wear will occur on the softer of the two tires and such excessive tread wear may be aggravated by the road surface conditions or the particular load conditions of the vehicle. It is important in this respect to keep the pressures relatively equal in dual wheel units; and for this purpose vehicle operators make frequent stops to check the pressure of the tires. Unequal tire pressure may occur in a dual wheel unit not only through pressure loss through a slow leak in one tire, but also due to unequal pressure buildup due to heat as a result of the road surface or load conditions.
U.S. Pat. No. 3,717,030, issued on Feb. 20, 1973 to Clarence L. McGhee (the present inventor) and Dennis C. Enders, discloses a device for the monitoring of tire pressures on a vehicle by mounting hub units on each wheel unit. Each hub unit includes a radio transmitter. A radio receiver is positioned leading to the vehicle operator. Each hub unit includes a bellows which is responsive to tire pressure so as to operate a visual pressure gauge on the hub unit which may be observed by the operator when the vehicle is stopped. It will also serve to energize the transmitter when the pressure decreases to a preselected value. For dual wheel units used on heavy duty vehicles, a common bellows may respond to the lower pressure of the two tires to indicate the lower pressure on the gauge and to transmit the fault signal. The dual wheel unit includes two bellows for actuating separate visual gauges for the two tires. A valve means is provided on the hub unit for equalizing tire pressures.
It is an object of the present invention to provide a system for detecting pressure loss and for providing a warning or fault signal to the vehicle operator when the pressure loss occurs.
It is another object of the present invention to provide a system which can transmit a signal to a receiver controlled by the operator of the vehicle.
It is still a further object of the present invention to provide a system that assures proper inflation pressure for the tires.
It is a further object of the present invention to provide a system that effectively maintains the pressure in dual tire units.
It is a further object of the present invention to provide a system which supplies its own power through the action of the rotating wheel for the purpose of operating the transmitter and receiver and associated solenoids.
It is still a further object of the present invention to provide a system which is easy to use, easy to install, and relatively inexpensive.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.